/*
 * Copyright 2000-2015 JetBrains s.r.o.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.intellij.util.containers;

import org.jetbrains.annotations.NotNull;
import org.jetbrains.annotations.Nullable;

import java.util.*;

/**
 * A drop-in replacement for {@link java.util.Stack} based on {@link ArrayList} (instead of {@link Vector})
 * and therefore is (1) not synchronized and (2) faster.
 *
 * @author max
 */
public class Stack<T> extends ArrayList<T> {
    public Stack() {
    }

    public Stack(int initialCapacity) {
        super(initialCapacity);
    }

    public Stack(@NotNull Collection<T> init) {
        super(init);
    }

    public Stack(@NotNull T... items) {
        for (T item : items) {
            push(item);
        }
    }

    public void push(T t) {
        add(t);
    }

    public T peek() {
        final int size = size();
        if (size == 0) throw new EmptyStackException();
        return get(size - 1);
    }

    public T pop() {
        final int size = size();
        if (size == 0) throw new EmptyStackException();
        return remove(size - 1);
    }

    @Nullable
    public T tryPop() {
        return isEmpty() ? null : pop();
    }

    public boolean empty() {
        return isEmpty();
    }

    @Override
    public boolean equals(Object o) {
        if (o instanceof RandomAccess && o instanceof List) {
            List other = (List) o;
            if (size() != other.size()) {
                return false;
            }

            for (int i = 0; i < other.size(); i++) {
                Object o1 = other.get(i);
                Object o2 = get(i);
                if (!(o1 == null ? o2 == null : o1.equals(o2))) {
                    return false;
                }
            }

            return true;
        }

        return super.equals(o);
    }
}